The influence of different roasting temperatures on the physical properties
of Arabica and Robusta coffee was investigated. Arabica (Rio Minas) of two
quality classes and Robusta coffee samples, roasted at 167, 171 and 175?C,
were used for this research. Bulk density, total weight loss, water
activity, texture and colour of coffee were determined. Total weight loss
increased, and bulk density of coffee beans decreased with increasing of
roasting temperature. Arabica 1st class with the highest weight and volume
also had the highest total weight loss and Robusta had the highest bulk
density. Coffee samples roasted at 175?C had significantly lower (P<0.05)
water activity values than samples roasted at 167?C and those changes
mostly affected mechanical properties of beans. The highest breaking force
values had Arabica 1st class, with lower share of black beans, roasted at
167?C and Arabica 2nd class roasted at 171 and 175?C, compared to other
samples roasted at the same temperatures. Robusta beans had the most brittle
and fragile texture. It can be concluded that texture of coffee depends on
the roasting temperature, type and class of coffee as well. L*, a*, and b*
colour parameters decreased as the roasting temperature increased, which
affected on coffee beverage colour defined as brown (167?C) and dark brown
(171?C and 175?C) with different share of yellowish, orange, reddish and
grey shades. Sensory analysis can be used as a good tool for a detailed
description of coffee colour, as an important indicator of quality,
especially in industrial conditions of coffee production.